1. Field of the Invention
The present application relates generally to tissue treatment systems and in particular to treatment of articular cartilage undergoing microfracture procedure.
2. Description of Related Art
Clinical studies and practice have shown that providing a reduced pressure in proximity to a tissue site augments and accelerates the growth of new tissue at the tissue site. The applications of this phenomenon are numerous, but application of reduced pressure has been particularly successful in treating wounds. This treatment provides a number of benefits, including faster healing and increased formulation of granulation tissue. Typically, reduced pressure is applied to tissue through a porous pad or other manifolding device. The porous pad contains cells or pores that are capable of distributing reduced pressure to the tissue and channeling fluids that are drawn from the tissue. The porous pad often is incorporated into a dressing having other components that facilitate treatment.
Articular cartilage is a highly organized avascular tissue composed of chondrocytes formed in an extracellular matrix. This tissue is extremely important to the normal, healthy function and articulation of joints. Articular cartilage enables joint motion surfaces to articulate smoothly with a very low coefficient of friction. It also acts as a cushion to absorb compressive, tensile, and shearing forces and, thus, helps protect the ends of bone and surrounding tissue.
Age, injury and wear, and cartilage disorders, such as osteoarthritis, affect millions of people throughout the world. Traumatic chondral injuries, for example, are common in sports and other activities that cause severe stress and strain to joints. Osteoarthritis is also a common condition that develops as cartilage wears, weakens, and deteriorates at the joint motion surfaces of bones. Indeed, it is currently believed that 85% of all Americans will develop degenerative joint disease as a result of normal activities that damage articular cartilage.
Articular cartilage is generally thin with an extremely low or insignificant blood flow and, as such, has a very limited ability to repair or heal itself Partial-thickness chondral defects, for example, cannot spontaneously heal. If these defects are left untreated, they often degenerate at the articular surface and progress to osteoarthritis. Full-thickness defects that penetrate subchondral bone can undergo some spontaneous repair if fibrocartilage forms at the defect. Even in spite of the formation of fibrocartilage, clinical evidence shows that full-thickness defects continue to degenerate and progress to osteoarthritis if these defects are left untreated.
Early diagnosis and treatment are crucial to hindering or stopping the progression of arthritis and degeneration of articular cartilage at joint motion surfaces. Today, depending on the grade of chondral damage, patients usually have several surgical options to repair or regenerate articular cartilage. Some current techniques to repair cartilage include implantation of chondrocytes, implantation of synthetic matrices and surgical intervention, with reattachment and reconstruction of the damaged tissue. None of these methods are totally satisfactory and they rarely restore full function or return the tissue to its native normal state. In addition, none of these methods are proven to regenerate cartilage in situ and in vivo.
Micro-fracture surgery is one treatment modality used to treat cartilage defects. This technique is a marrow-stimulating arthroscopic procedure to penetrate the subchondral bone to induce fibrin clot formation and the migration of primitive stem cells from the bone marrow into the defective cartilage location. Generally, the base of the defective area is shaved or scraped to induce bleeding. An arthroscopic awl or pick is then used to make small holes or microfractures in the subchondral bone plate. The end of the awl is manually struck with a mallet to form the holes while care is made not to penetrate too deeply and damage the subchondral plate. The holes penetrate a vascularisation zone and stimulate the formation of a fibrin clot containing pluripotential stem cells. The clot fills the defect and matures into fibrocartilage.
While microfracture surgery has a high success rate, patients cannot return to sports or other intense activities for about 4 months, even with the help of physical therapy. Additionally, the tissue that forms in the defect is primarily fibrocartilage (this constitutes a repair process whereby a different tissue type is formed), which does not have the same functional characteristics of articular (hyaline) cartilage. As such, there is currently an acute need for a method that leads to more of a regenerative response (forms the same type of tissue that was damages, for example, hyaline cartilage) rather than a repair response and that reduces the overall time of healing.
It would therefore be advantageous to provide devices, methods and systems to promote healing and/or tissue regeneration after microfracture surgery. Such devices, methods and systems would decrease healing time, and lead to better functional outcomes thus increasing the patient's quality of life and enable a more rapid return to normal daily activities.